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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
If there were no rules on the input, then that's probably a good idea. However, the description of the kata clearly states that the input will always be a non-begative integer, so the extra defensive code is unnecessary in this situation.
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